This kind of air bag apparatus includes, for example, a structure in which an air bag housed along a roof side rail is inflated and deployed in a curtain-like shape along a side wall of a vehicle compartment by a gas supplied from an inflator so as to protect a head portion of an occupant, and a structure in which an air bag housed in an instrument panel is inflated and deployed toward an inner portion of the vehicle compartment due to the gas supplied from the inflator so as to protect a head portion and a chest portion of the occupant.
The conventional air bag apparatus mentioned above includes a structure in which an inner tube is internally provided along a gas passage (an inflow portion) of an air bag so as to restrict bag damage by the gas supplied to the air bag from the inflator, for example, as disclosed in Japanese Patent Application Laid-Open No. 11-321536, and a structure in which a cylindrical body is provided along a gas passage of an air bag so as to restrict bag damage by a gas supplied to the air bag from an inflator, for example, as disclosed in Japanese Patent Application Laid-Open No. 11-301394 and 2000-127886.
In these air bag apparatus, since the inner tube or the cylindrical body (a protecting member) mentioned above is provided in the gas passage of the air bag so as to restrict bag damage by the gas supplied to the air bag from the inflator, there is a risk that the inner tube or the cylindrical body mentioned above inhibits folding of the air bag, making it more difficult to house the air bag in the vehicle and cause a cost increase of the air bag apparatus.
On the contrary, in the air bag apparatus, it is necessary to satisfy various requirements in view of inflating and deploying performance of the air bag (a requirement of making a period of time after starting inflation and deployment until completion equal to or shorter than a set time, a requirement of maintaining an initial internal pressure after starting inflation and deployment until completion equal to or greater than a high set pressure, a requirement of maintaining an internal pressure equal to or greater than a low set pressure for a predetermined time after an initial predetermined time has elapsed after completing inflation and deployment, and the like).
In order to reduce the period of time for completing inflation and deployment of the air bag and increase the initial internal pressure, there is generally employed a countermeasure of increasing a gas supplying capacity of the inflator. However, when increasing the gas supplying capacity of the inflator, the bag damage is increased and it is impossible to increase a time of maintaining the internal pressure. Accordingly, it is necessary to sufficiently apply a coating for keeping airtightness, for example, onto a surface of the air bag so as to restrict bag damage and increase airtight performance, or it is necessary to increase a gas supply capacity of the inflator in addition to increasing airtight performance of the air bag. In view of this, improving the inflating and deploying performance of the air bag and reducing a cost is contradictive. Such a problem can be resolved by restricting the bag damage of the air bag by means capable of being realized at a low cost.